Droughts projection over the Niger and Volta River basins of West Africa at specific global warming levels

Abstract

This study investigates possible impacts of four global warming levels (GWLs: GWL1.5, GWL2.0, GWL2.5, and GWL3.0) on drought characteristics over Niger River basin (NRB) and Volta River basin (VRB). Two drought indices—Standardized Precipitation Index (SPI) and Standardized Precipitation‐Evapotranspiration Index (SPEI)—were employed in characterizing droughts in 20 multi‐model simulation outputs from the Coordinated Regional Climate Downscaling Experiment (CORDEX). The performance of the simulation in reproducing basic hydro‐climatological features and severe drought characteristics (i.e., magnitude and frequency) in the basins were evaluated. The projected changes in the future drought frequency were quantified and compared under the four GWLs for two climate forcing scenarios (RCP8.5 and RCP4.5). The regional climate model (RCM) ensemble gives a realistic simulation of historical hydro‐climatological variables needed to calculate the drought indices. With SPEI, the simulation ensemble projects an increase in the magnitude and frequency of severe droughts over both basins (NRB and VRB) at all GWLs, but the increase, which grows with the GWLs, is higher over NRB than over VRB. More than 75% of the simulations agree on the projected increase at GWL1.5 and all simulations agree on the increase at higher GWLs. With SPI, the projected changes in severe drought is weaker and the magnitude remains the same at all GWLs, suggesting that SPI projection may underestimate impacts of the GWLs on the intensity and severity of future drought. The results of this study have application in mitigating impact of global warming on future drought risk over the regional water systems.

Projections of indices of daily temperature and precipitation based on bias-adjusted CORDEX-Africa regional climate model simulations

“…Here, we present a dataset of daily, bias-adjusted temperature and precipitation projections for continental Africa based on the large CORDEX ensemble, which can be useful for studies of impact of climate change on several sectors (e.g. Warnatzsch and Reay 2019;Rohat et al 2019;Sawadogo et al 2020;Oguntunde et al 2020;Laux et al 2021; see also https:// www. csag.…”

Impact of Stratospheric Aerosol Geoengineering on Meteorological Droughts in West Africa

“…GLENS simulations are grid monthly data with 0.95° longitude × 1.25° latitude resolution. It uses prescribed greenhouse gas forcing concentrations following the representative concentration pathway 8.5 (RCP8.5, i.e., a high anthropogenic emission scenario) [24]. These simulations were conducted using the NCAR Community Earth System Model with the Whole Atmosphere Community Climate Model as its atmospheric component (CESM1 WACCM) [32] (Table 1).…”

“…In this section, we assess the performance of the CESM1 (WACCM) simulations to reproduce the observed precipitation in West Africa. The assessment of precipitation is very important because the accuracy and reliability of the future simulations of the meteorological drought index depend on how well the models capture the historical precipitation [24]. Figure 2 presents the spatial distribution of observed, simulated and observedsimulated seasonal and annual mean rainfall in West Africa.…”

“…As most people in West Africa are involved in climate-sensitive sectors of the economy, any change in the climate that enhances drier conditions may increase the vulnerability to climate risks over the region. Any substantial rainfall deficit usually devastates socio-economic activities for a long period because agriculture, hydro-electric power, and river basin management depend on rainfall [24]. Recurrent drought is a complex phenomenon that may adversely affect water supplies and crop and livestock production, causing food insecurity and the disruption of the livelihood activities of a region [25][26][27].…”

“…Indeed, an increase in drought intensity and spatial extent are projected related to the present-day over the Volta River Basin using standardized precipitation index (SPI) and the standardized precipitation and evapotranspiration index (SPEI) using an ensemble of climate models under climate change scenarios [27]. Drought frequency (events per decade) may be magnified by a factor of 1.2 (2046-2065) to 1.6 (2081-2100) compared to the present-day episodes in the basin [24,27]. They also projected an increase in the magnitude and frequency of severe droughts over both the Niger River and Volta River basins at all global warming levels.…”